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Michael Scheel, Linda J. Lanyon, Deborah Giaschi, Jason J. Barton; The organization of inter-hemispheric projections from areas 17 and 18 in the human splenium, studied with DTI probabilistic fiber tracking. Journal of Vision 2009;9(8):772. doi: https://doi.org/10.1167/9.8.772.
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© ARVO (1962-2015); The Authors (2016-present)
Animal tracer studies show a clear pattern of organization of intercortical callosal connections between early visual areas of the left and right hemisphere. To investigate if a similar organization is evident for human occipital cortex we performed diffusion tensor imaging with probabilistic fiber tracking in 10 healthy volunteers.
Areas 17 and 18 were defined in two different ways, using high-resolution structural T1-weighted MRI scans: (1) anatomically through defined masks of upper and lower early visual cortex around the calcarine fissure, and (2) through masks of areas 17 and 18 from histological probability maps. Diffusion-tensor imaging data were analyzed by probabilistic tracking methods in FSL.
Our results first confirm through cortical-connectivity-based hard segmentation of the entire corpus callosum that connections between areas 17 and 18 of both hemispheres are confined to the lower part of the splenium. Second, there is an orderly representation of the callosal projections of the upper and lower hemifields of both areas 17 and 18 in the splenium. This mirrors the anatomic relations of these regions in the occipital lobe: fibers from dorsal area 18, inferior bank of area 17, superior bank of area 17, and ventral area 18 are layered from antero-dorsal to postero-ventral. We conclude that the quadrantic organization of areas 17 and 18 is preserved in their callosal projections through the splenium.
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